LR45 flight crew, during ILS final approach, while the aircraft was being flown on autoplt, has the ...

Attributes
ACN	577277
Time
Date	200303
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : mmj.vortac
State Reference	PA
Altitude	msl bound lower : 3000 msl bound upper : 3250
Environment
Flight Conditions	VMC
Weather Elements	Rain Windshear
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : pit.tracon
Operator	general aviation : corporate
Make Model Name	Learjet 45
Operating Under FAR Part	Part 91
Navigation In Use	ils localizer & glide slope : 32 other other vortac
Flight Phase	descent : approach
Route In Use	approach : instrument precision arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 60 flight time total : 6000 flight time type : 400
ASRS Report	577277
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : overcame equipment problem flight crew : overrode automation
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Aircraft

Narrative:

While on a final vector from pittsburgh approach to intercept the final approach course for ILS 32, we were given turn left to 300 degree maintain 3000, cleared ILS 32 approach. At that point, I armed the approach mode. The automatic pilot was engaged during the entire approach (while being vectoring). At 7 DME from mmj, the airplane, while on autoplt, pitched up violently and started an attempt to climb up to the altitude (from our position) to intercept the glideslope. ATC gave us 3000 ft, but the aircraft, on autoplt, tried to catch or intercept the glideslope from our location. In the pitch-up action caused by the autoplt, the aircraft climbed 200 ft to 250 ft. As soon as I saw the autoplt pitching the aircraft nose up to meet the glideslope I disconnected the autoplt immediately and started to pitch the aircraft down to assigned altitude of 3000 ft. This aircraft (LR45) has honeywell avionics and there is a known problem with the software in the problem. This has occurred several times before. The problem does not occur every time, but has happened often, and with other LR45's in our fleet and others. The aircraft while on autoplt pitches up very suddenly and you immediately disconnect it and start pushing the nose over causing negative G's (passengers came out of seats) to re-establish altitude. Callback conversation with reporter revealed the following information: reporter stated that the aircraft departed the selected altitude programmed in the 'altitude window' prior to the glide slope becoming active. Additionally, the reporter added that lear corporation has published a caution that the glide slope may become unusable when the flight crew transmits on the VHF radio. Although this analyst questioned the reporter regarding the loss of glide slope signal during VFR WX and the possibility that the 'ILS safe zone' may have been penetrated, the reporter indicated that this phenomenon has been reported by other flight crews during all types of WX, when the 'ILS safe zone' was in affect. The reporter also stated that this anomaly only occurs during specific runway/ILS comrinations (ie: ILS 32 pit).

Original NASA ASRS Text

Title: LR45 FLT CREW, DURING ILS FINAL APCH, WHILE THE ACFT WAS BEING FLOWN ON AUTOPLT, HAS THE ACFT PITCH-UP DEPARTING THE SELECTED ALT.

Narrative: WHILE ON A FINAL VECTOR FROM PITTSBURGH APCH TO INTERCEPT THE FINAL APCH COURSE FOR ILS 32, WE WERE GIVEN TURN L TO 300 DEG MAINTAIN 3000, CLRED ILS 32 APCH. AT THAT POINT, I ARMED THE APCH MODE. THE AUTO PLT WAS ENGAGED DURING THE ENTIRE APCH (WHILE BEING VECTORING). AT 7 DME FROM MMJ, THE AIRPLANE, WHILE ON AUTOPLT, PITCHED UP VIOLENTLY AND STARTED AN ATTEMPT TO CLB UP TO THE ALT (FROM OUR POS) TO INTERCEPT THE GLIDESLOPE. ATC GAVE US 3000 FT, BUT THE ACFT, ON AUTOPLT, TRIED TO CATCH OR INTERCEPT THE GLIDESLOPE FROM OUR LOCATION. IN THE PITCH-UP ACTION CAUSED BY THE AUTOPLT, THE ACFT CLBED 200 FT TO 250 FT. AS SOON AS I SAW THE AUTOPLT PITCHING THE ACFT NOSE UP TO MEET THE GLIDESLOPE I DISCONNECTED THE AUTOPLT IMMEDIATELY AND STARTED TO PITCH THE ACFT DOWN TO ASSIGNED ALT OF 3000 FT. THIS ACFT (LR45) HAS HONEYWELL AVIONICS AND THERE IS A KNOWN PROB WITH THE SOFTWARE IN THE PROB. THIS HAS OCCURRED SEVERAL TIMES BEFORE. THE PROB DOES NOT OCCUR EVERY TIME, BUT HAS HAPPENED OFTEN, AND WITH OTHER LR45'S IN OUR FLEET AND OTHERS. THE ACFT WHILE ON AUTOPLT PITCHES UP VERY SUDDENLY AND YOU IMMEDIATELY DISCONNECT IT AND START PUSHING THE NOSE OVER CAUSING NEGATIVE G'S (PAXS CAME OUT OF SEATS) TO RE-ESTABLISH ALT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE ACFT DEPARTED THE SELECTED ALT PROGRAMMED IN THE 'ALT WINDOW' PRIOR TO THE GLIDE SLOPE BECOMING ACTIVE. ADDITIONALLY, THE RPTR ADDED THAT LEAR CORPORATION HAS PUBLISHED A CAUTION THAT THE GLIDE SLOPE MAY BECOME UNUSABLE WHEN THE FLT CREW TRANSMITS ON THE VHF RADIO. ALTHOUGH THIS ANALYST QUESTIONED THE RPTR REGARDING THE LOSS OF GLIDE SLOPE SIGNAL DURING VFR WX AND THE POSSIBILITY THAT THE 'ILS SAFE ZONE' MAY HAVE BEEN PENETRATED, THE RPTR INDICATED THAT THIS PHENOMENON HAS BEEN RPTED BY OTHER FLT CREWS DURING ALL TYPES OF WX, WHEN THE 'ILS SAFE ZONE' WAS IN AFFECT. THE RPTR ALSO STATED THAT THIS ANOMALY ONLY OCCURS DURING SPECIFIC RWY/ILS COMRINATIONS (IE: ILS 32 PIT).

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

LR45 flight crew, during ILS final approach, while the aircraft was being flown on autoplt, has the aircraft pitch-up departing the selected altitude.